1. Field of the Invention
This invention relates generally to ramps for loading and unloading vehicles; and, more particularly to a strong light-weight ramp structure that is foldable and includes a structure for positioning the ramp and holding it in place during a loading or unloading operations.
2. State of the Prior Art
Various types of ramp structures have been devised and used for loading and unloading vehicles on other vehicles for transportation. Many of these prior ramp structures are hinged or otherwise mounted to the transport vehicle, and thus cannot be readily moved for use with other transport vehicles. Further, when so mounted, the transport vehicle cannot be readily used for other purposes without the mounted ramp being in the way.
For transporting a class of relatively light vehicles, such as snowmobiles, all-terrain vehicles, lawn mowers, motorcycles, and the like, transport vehicles often include towed trailers, pickup trucks, and wagons. These types of transport vehicles often have a variety of uses, only one of which may be to transport those light-weight vehicles, and mounted loading structures are unacceptable.
One type of loading apparatus involves a support surface that is movably mounted to the transport vehicle such that the support surface can be lowered to ground level to allow a vehicle to be placed thereon, and then can be raised to the level of the bed of the transport vehicle. The raising mechanisms include hydraulics, power driven cable and pulley assembles, and other forms of power structures. All of these devices add weight to the transport vehicle, remain in place unless extensive removal operations are done, are limited in use to a vehicle that is adapted to work with it, and may not be readily used with other transport vehicles.
Folding ramp structures have been developed such that the ramp is hingedly mounted to the transport vehicle, and is laterally hinged in two or more sections such that when the ramp is raised, it folds back upon itself so that it does not protrude upwardly to an unacceptable height. These types of folding ramps are most often used with very light-weight apparatus, such as lawn mowers, because the laterally folding structure is difficult to fabricate with substantial longitudinal rigidity. Such mounted, laterally folding ramps cannot readily be moved for use with other transport vehicles.
Removable ramps have long been used with transport vehicles where the ramp has hooks or other engaging members mounted at one end of the ramp. These members are arranged for cooperating with some structure on the transport vehicle to hold the end of the ramp in place when engaged. These structures are often used with livestock trucks, and while effective, are often difficult to engage and are not readily portable to other transport vehicles.
The simplest prior art ramps are constructed of planks with one end arranged to rest on the ground and the other end to be supported on the bed of the transport vehicle. While simple, this type of ramp is dangerous in that the planks routinely slide forward when loading, such that the ground end flies up when the loaded vehicle moves to the bed of the transport vehicle; and routinely slide back when unloading, such that the end supported on the bed slips off and allows the ramp and the unloading vehicle to fall to the ground. Neither of these results is acceptable.
None of the prior art ramp structures are adequate or designed to provide safety and flexibility of use with a variety of transport vehicles. Various prior art ramps have been constructed of wood, which decays and loses strength, or steel, which is heavy and tends to rust. Most are too heavy to be used by anyone other than very strong people.